Condenser transmitter



Nov. 8, 1927. v

A'HUND 1,648,689

CONDENSER TRANSMITTER Filed April 10. 1926 I law-1' 000 00 00000000000000000000 w 00000000000 0000 1 0000000000 000000 00000 000000000000ooooooooooooooooooo o oooooooooooooooo ooo 000000000000000000000ooooooooooooooooooooooa Z 00o 0000000o0000 0000000 00o00o0o00o00o0000000 00000000000 00000 000000 OOOOOOOOOOOOOOOOOOOOO000000000000 000000000 1 0000000 0 0000000 0 1 000000000 0000000000000000 0 000000000 1 000000000000000 ATTORNEY e Patented Nov. '8, 1927-.

UNITED STATES AUeus'r noun, or nn'rnnsna, MARYLAND, Assienon 'ro NEWYORK,

WIRED namo, Inc, or.

N. Y., A conrona'rron'or DELAWARE.

CONDENSER rnnns arrrnn. I I

I Application llled April 10,

My. invention .relates broadly to voice modulating apparatus and moreparticularly to a condenser type sound detector and transmitter. I

One of the objects of my invention isto provide an extremely sensitivesound trol circuit of an electron tube ampliher for modulatingelectrical with sound vibrations.

Another object of my invention is' to pro-- vide a construction ofcondenser transmitter in which sound-at relatively great distances maybe detected and utilized to control the circuit of a condensertransmitter for modulating electrical currents with substantially nodlstortion.

Another object of my invention is to provide a simplified constructionof electrostatic transmitter in whicha sound distribution plate is,provided for uniformly distrib uting sound vibrations over the area of arelatively flexible plate which .may be chan ed in position by theimpinging of soun .waves thereagainst, the operation of an electron tubesystem. Another object of my invention is to provide aninexpensiv'econstruction of condenser transmitter which may be readily manufacturedfrom a relatively small number of parts and yet will have the propertyof great sensitivity and ability to 'efiectively control theoperation ofan electron tube system for the production of modulated current, in ac-3:, cordance with sound vibrations.

My invention will more clearly understood from the specificationhereinafter following b reference to the accompanying drawings w erein:Figure 1 is a front elevation of the condenser transmitter embodying theprinciples of my invention; Fig. 2 is a cross-sectional view takenthrough the condenser transmitter on line ,2-2 thereof; and Fig. 3 showsthe electrical connections of the condenser transmitter of my inventionwith anv electron tube system. c

.Heretnfore 1n the art condenser trans- .mitters have been relativelyinsensitive as compared with the usual carbon microphone transmitter.Prior constructions of condenser transmitters have been relativelycomplicated-and expensive to manufacture. My condenser transmitterconstruction 'is'relatively simple and requires only a small detecv torand transmitter for operation in'the concurrents in accordance Icondenser transmitter.

plates and ring members being secured for controlling 1926. Serial No.101,203.

number of parts and yet'y the device is highly sensitive to soundvibrations and has been used for the dete( ;tio1rof.- very sounds andthemodulation vof electrical currents in accordance with the soundvibrations.

Referring to the drawings in more detail reference character 1designates one of the end plates constituting one electrode of theReference character 2 designates an opposite end. plate of the condensertransmitter which is spaced-from the plate l by means of concentmcallyposi tioned insulated ring members 3 and 5, the

together by means of bolt members 6 which pass through the severalmembers, the bolts being secure which bear upon bers '7, located in theplate member, 1. In this manner the plate member 1 is substantiallyinsulated from the plate member 2. flexible sheet of 'metal 8 isstretched over the annular flange or bead 4 of the ring member 3- andhas its outer periphery 9 PP ed between the insulated ring members 3 and5 stretching the sheetB in the manner of a drum. ;The plate 8 is formedof very thin metal foil which is readily moved by sound vibrationsimpinging thereagainst. The plate 8 forms the other electrode of thecondenser detector. The ring member 5 telescopes over the ring member3"in securing the foil 8 over the head portion 4. The ring members 3 and5 fit snugly together in the manner of hoops for clamping the flexiblefoil 8 therebetween. The plate member 1 is provided witha plurality ofapertures represented at 10 positioned throughout the area of platemember 1 which is bounded feeble d therein by means of nuts.

the insulated bushing mem- 1 by the dotted line 11- forming a space or 7gap 12 immediately over the flexible foil sheet 8.

In Fig. 3 I have shown the electrical connections of the condensertransmitter in an electron tube circuit. The electron tube circuitcomprises tubes 1 1, 15 and 16 in the form of a resistance capacitycoupled amplifier'whose input circuit is controlled by the condensertransmitter as illustrated. Plate 1 of the condenser transmitter (01'detector sensitivity) connects with the grid electrode of the input.circuit, while plate 8 connects with the filament electrode of tube 14;.A high potential direct current is unelectrodes.

pressed across the electrodes of the condenser transmitter. Thispotential may be derived from the B-battery source or it may be obtainedfrom an independent source.

In the operation of the condenser transmitter the sound entersthrough'the many circular apertures 10 provided in the metallic plate 1.In a preferred embodiment of my invention these apertures have a diameter of about-{ of an inch and their centers are spaced of an inch, thatis, their centers are the corners of small squares whose sides is of aninch long. This leaves enough active material in plate 1 for thecondenser action and admits the sound very uniformly. In one of mydesigns I employan outside diameter of 5" and an efl'ective insidediameter of 4".

For the best results I apply about 200 volts across the condenserelectrodes for establishing the normal charges on the condenser Thesound vibrations which impinge upon the flexible foil sheet 8 by passmgthrough the apertures the flexible sheet 8, for varying the syfagcialrelation between plate 1 and flexible sheet 8 for varying'theelectrostatic capacitytherebetween.

The condenser transmitter of my invention has proven so sensitive that Ihave successfully detected the speech of a person talking in an ordinarytone of voice 150 feet distant from the vtransmitter. I have detectedthe disturbances offered by approaching aircraft at a distance ofseveral miles, and other important a plications of the invention havebeen marl the initial sound disturbance is relatively slight, so slightin fact that the ear would normally not perceive such sounds, and yetWhere positive detection of these slight sounds has been accomplished.Mention may be made herein of the ready adaptability of the invention inthe faithful recording of music and voice records, detectophone pick-upand devices for assisting the deaf to hear. Many other applications ofthe invention will readily suggest themselves to those skilled in theart. 7

While I have described my invention in a certain preferred embodiment, Idesire it to be understood that modifications may be 10 bodily move e ininstances where b made and that no limitations upon the invention areintended other than are imposed by the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is as follows:

1. A condenser transmitter comprising in combination a pair of insulatedring members, one of said ring members having an annular flange and theother of said ring members fitting around said annular flange in thenature of a hoop, a flexible sheet of metal stretched over said annularflange and gripped between, said ring members,and an apertured--.conductive plate supported by said ring members in spacedrelationship to said flexible plate memberfor permitting the freepassage of sound vibrations to said flexible plate member for, varyingthe electrostaticcapacity between said conductive plate member and saidflexible plate member.

2. A condenser transmitter comprising in combination a tioned insulatedhoop members fitting one over the other, a sheet of flexible metalstretched over said hoop members forming a drum-like surface, and anapert-ured metallic plate member secured to saidhoop members in spacedrelation to said sheet of flexible metal whereby sound vibrations may bedirected against said sheet of flexible metal or varying the spacialrelation between said apertured plate member and said flexible sheetmember.

3. A condenser transmitter comprising in combination a pair of metallicplate memers, a pair of insulated rim members telescoped one over theother, and a flexible metallic sheet stretched between said rim membersand directly parallel with one of said said metallic plate permittingthe impingement of sound vibrations against said flexible sheet memberfor member and said flexpair of concentrically posi-

